PARIS (Reuters) - The head of a French union blamed for months of violence-marred demonstrations said on Thursday it would stage more street marches against labor law reform next week, and accused the government of trying to discredit legitimate protest.

The riposte from CGT union leader Philippe Martinez followed running battles in the streets of Paris and threats by President Francois Hollande to ban further marches.

As he spoke, a court official said around 40 people arrested in Tuesday's clashes were sent to face a judge in Paris, risking immediate sentences of months in prison for public order offences.

"It's as if the CGT is to blame for everything going on in this country," said Martinez, whose hardline union, one of the largest in France, plans more protests on June 23 and June 28.

"The government must stop throwing oil on the fire," he said, adding that attempts by Prime Minister Manuel Valls to pin blame for violence on the CGT risked exacerbating tensions.

The union says the labor law change will undermine labor protection while the government says it will help develop grassroots union representation by devolving negotiation of pay and conditions to the workplace from sector-level.

After months of at times confrontational protests, violence escalated dramatically at a Paris city center rally on Tuesday when hundreds of mostly masked rioters engaged in running battles with police, smashing shopfronts and daubing buildings with anti-capitalist slogans.

The trouble caused largely by gangs of youths sparked outrage when they smashed windows of the capital's Necker children's hospital.

The CGT head rejected government accusations that his union was turning a blind eye to troublemakers in its ranks, but he was put on the defensive by Paris police reports that up to 200 CGT members took part in altercations.

Martinez told RTL radio the scenes in question involved people defending themselves against a police charge that should have been directed at hardcore rioters but was instead directed at the main marching line.

"When that kind of thing happens everybody does what he can to defend himself. That kind of charge is often fairly violent."

Interior Minister Bernard Cazeneuve said Martinez should condemn violence more clearly and exclude troublemakers from his union.

Police used water cannon, teargas and baton charges against gangs of mostly black-clad rioters, arresting around 60 people.

Paris police said that, in all, between 800 and 1,000 people were involved in skirmishes, including several Germans and Italians.